U.S. patent number 7,712,735 [Application Number 11/858,468] was granted by the patent office on 2010-05-11 for device for unstacking postal items with optimized management of unstacking conditions.
This patent grant is currently assigned to Solystic. Invention is credited to Stephane Ambroise, Pierre Chorier-Pichon, Stephane Samain.
United States Patent |
7,712,735 |
Chorier-Pichon , et
al. |
May 11, 2010 |
Device for unstacking postal items with optimized management of
unstacking conditions
Abstract
An unstacker device for unstacking flat objects comprises a
motor-driven feed magazine controlled so as to move flat objects in
a stack and on edge facing an unstacking head provided with a
motor-driven drive having a perforated belt and a suction chamber,
which motor driven drive is actuated so as to separate a current
first object from the stack and so as to eject it in a direction
that is transverse to the direction in which the stack of flat
objects is moved, in which device the motor-driven drive is
actuated and stopped each time a current object is unstacked, and
the stack of flat objects is straightened up in the magazine in
response to detection of signals delivered by a plurality of
sensors disposed in the unstacking head. The sensors are disposed
in the unstacking head in a manner such as to deliver signals
indicating that the current object is presented appropriately
relative to the unstacking head, and the drive of the unstacking
head is actuated if the signals indicate that the current object is
presented appropriately.
Inventors: |
Chorier-Pichon; Pierre (Romans,
FR), Ambroise; Stephane (Valence, FR),
Samain; Stephane (Chabeuil, FR) |
Assignee: |
Solystic (Gentilly Cedex,
FR)
|
Family
ID: |
37944304 |
Appl.
No.: |
11/858,468 |
Filed: |
September 20, 2007 |
Prior Publication Data
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|
|
|
Document
Identifier |
Publication Date |
|
US 20080073827 A1 |
Mar 27, 2008 |
|
Foreign Application Priority Data
|
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|
|
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Sep 21, 2006 [FR] |
|
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06 53854 |
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Current U.S.
Class: |
271/153;
414/795.7; 414/795.2; 271/214; 271/213; 271/159; 271/158; 271/157;
271/150; 271/149 |
Current CPC
Class: |
B65H
3/124 (20130101); B65H 3/46 (20130101); B65H
2701/1916 (20130101); B65H 2511/514 (20130101); B65H
2511/514 (20130101); B65H 2220/01 (20130101); B65H
2220/09 (20130101) |
Current International
Class: |
B65H
1/18 (20060101) |
Field of
Search: |
;271/149,150,153,157,158,159,213,214 ;414/795.2,795.7 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Mackey; Patrick H
Assistant Examiner: Gokhale; Prasad V
Attorney, Agent or Firm: Rothwell, Figg, Ernst &
Manbeck, P.C.
Claims
What is claimed is:
1. An unstacker device for unstacking flat objects, which device
comprises a motor-driven feed magazine controlled so as to move
flat objects in a stack and on edge facing an unstacking head
provided with a motor-driven drive having a perforated belt and a
suction chamber, which motor-driven unstacking head drive is
actuated so as to separate a current first object from the stack
and so as to eject it in a direction that is transverse to the
direction in which the stack of flat objects is moved, in which
device the motor-driven unstacking head drive is actuated and
stopped each time a current object is unstacked, and the stack of
flat objects is straightened up in the magazine in response to
detection of signals delivered by a plurality of sensors disposed
in the unstacking head, a first sensor being disposed to detect
presence of a bottom portion of the current object facing the
unstacking head, a second sensor being disposed to detect presence
of a first intermediate portion of the current object facing the
unstacking head, said first intermediate portion being situated
above said bottom portion of the current object, wherein a third
sensor is disposed to detect presence of a second intermediate
portion of the current object facing the unstacking head, said
second intermediate portion being situated above said first
intermediate portion of the current object, said sensors being
disposed in the unstacking head in a manner such as to deliver
signals indicating that said current object is presented
appropriately relative to the unstacking head, wherein said
unstacker device further comprises a control unit connected with
said sensors, said control unit being programmed for actuating the
drive of the unstacking head so as to separate a current first
object from the stack if the signals indicate that the current
object is presented appropriately and for stopping the drive of the
unstacking head if the signals indicate that the current object is
presented inappropriately.
2. An unstacker device according to claim 1, in which the
unstacking head comprises a metal sheet provided with two openings
side-by-side.
3. An unstacker device according to claim 1, in which the first
sensor is a flag mechanical sensor, the second sensor is a
reflection optical sensor, and the third sensor is a reflection
optical sensor.
4. An unstacker device according to claim 2, in which the first,
second, and third sensors are aligned vertically in the unstacking
head between said two openings.
5. An unstacker device according to claim 1, in which said
plurality of sensors further includes a fourth sensor disposed to
detect presence of a flat object in said direction that is
transverse to the direction in which the stack of flat objects
moves.
6. An unstacker device according to claim 5, in which said fourth
sensor is an optical barrier sensor.
7. An unstacker device according to claim 1, in which the feed
magazine comprises a drop-forming feed disposed between a main
conveyor belt with a motor-driven drive and the unstacking head,
and a paddle with a motor-driven drive, said paddle being suitable
for being moved along the main conveyor belt, the drop-forming feed
being provided with secondary conveyor belts with a motor-driven
drive, the control unit acting on the motor-driven drives of the
main conveyor belt, of the paddle, and of the secondary conveyor
belts so as to present the current object appropriately relative to
the unstacking head.
8. An unstacker device according to claim 7, in which the control
unit is arranged to change the speeds and the directions of the
motor-driven drives of the feed magazine in order to present the
current object appropriately relative to the unstacking head.
9. An unstacker device according to claim 8, in which the control
unit is arranged to trigger an alarm at the end of a certain time
for which the control unit has been acting on the motor-driven
drives of the main conveyor belt, of the paddle, and of the
secondary conveyor belts without obtaining appropriate presentation
of the current object relative to the unstacking head.
10. A machine for handling postal items, said machine including an
unstacker device according to claim 1.
11. An unstacker device for unstacking flat objects, which device
comprises a motor-driven feed magazine controlled so as to move
flat objects in a stack and on edge facing an unstacking head
provided with a motor-driven drive having a perforated belt and a
suction chamber, which motor-driven drive is actuated so as to
separate a current first object from the stack and so as to eject
it in a direction that is transverse to the direction in which the
stack of flat objects is moved, in which device the motor-driven
drive is actuated and stopped each time a current object is
unstacked, and the stack of flat objects is straightened up in the
magazine in response to detection of signals delivered by a
plurality of sensors disposed in the unstacking head, a first
sensor being disposed to detect presence of a bottom portion of the
current object facing the unstacking head, a second sensor being
disposed to detect presence of a first intermediate portion of the
current object facing the unstacking head, said first intermediate
portion being situated above said bottom portion of the current
object, wherein a third sensor is disposed to detect presence of a
second intermediate portion of the current object facing the
unstacking head, said second intermediate portion being situated
above said first intermediate portion of the current object, said
sensors being disposed in the unstacking head in a manner such as
to deliver signals indicating that said current object is presented
appropriately relative to the unstacking head, and wherein the
drive of the unstacking head is actuated if the signals indicate
that the current object is presented appropriately, wherein the
feed magazine comprises a drop-forming feed disposed between a main
conveyor belt with a motor-driven drive and the unstacking head,
and a paddle with a motor-driven drive, said paddle being suitable
for being moved along the main conveyor belt, the drop-forming feed
being provided with secondary conveyor belts with a motor-driven
drive, the control unit acting on the motor-driven drives of the
main conveyor belt, of the paddle, and of the secondary conveyor
belts so as to present the current object appropriately relative to
the unstacking head, and wherein the control unit is arranged to
change the speeds and the directions of the motor-driven drives of
the feed magazine in order to present the current object
appropriately relative to the unstacking head, and wherein the
control unit is arranged to trigger an alarm at the end of a
certain time for which the control unit has been acting on the
motor-driven drives of the main conveyor belt, of the paddle, and
of the secondary conveyor belts without obtaining appropriate
presentation of the current object relative to the unstacking head.
Description
FIELD OF THE INVENTION
The invention relates to an unstacker device for unstacking flat
objects, which device comprises a motor-driven feed magazine
controlled so as to move flat objects in a stack and on edge facing
an unstacking head provided with a motor-driven drive. The
motor-driven drive, which includes a perforated belt and a suction
chamber, is actuated so as to separate a current first object from
the stack and so as to eject it in a direction that is transverse
to the direction in which the stack of flat objects is moved.
BACKGROUND OF THE INVENTION
The invention relates more particularly to a device for unstacking
postal items, such as letters and large-format flat objects or
"flats", in a postal sorting machine, for example.
Patent Document FR 2 797 856 discloses a device for unstacking
postal items that is provided with a main magazine 1 having a belt.
As shown in FIG. 1, the main magazine 1 comprises, in particular, a
motor-driven conveyor belt 2 on which an operator disposes the
postal items 3 in a stack and on edge, and a paddle 4 that is also
motor-driven, that extends in a substantially vertical plane, and
that is moved so as to push the back of the stack in the direction
indicated by the arrow 6 facing the unstacking head 5.
The postal items in the stack are held laterally by a jogger edge 7
that extends in a substantially vertical plane along one edge of
the conveyor belt 2. The substantially plane unstacking head 5
extends in a vertical plane that is transverse to the direction
that is indicated by the arrow 6 and in which the stack of postal
items 3 moves on the conveyor belt 2, and said unstacking head is
suitable for separating the current first postal item at the front
of the stack in the transverse direction indicated by the arrow 8
that is perpendicular to the arrow 6.
The unstacking head 5 is provided with two substantially
rectangular openings in which a perforated belt 9 and one or more
suction chambers or suction nozzles (not shown) are driven by
motors, which openings co-operate to take hold of the first postal
item in the stack by suction and to move it in the direction
indicated by the arrow 8.
In operation, the stack of postal items 3 disposed in the main
magazine 1 is moved by the stepper-type motor-driven drives of the
conveyor belt 2 and of the paddle 4, which drives are actuated at
the same speed. The first postal item at the front of the stack of
postal items is thus brought into abutment against the unstacking
head 5 so that that current postal item of the stack is caused to
bear against the unstacking head 5 and is separated from the stack
by the combined effect of the suction from the nozzles and of the
movement of the perforated belt 9. The postal item is then nipped
between two deformable wheels 10 disposed in alignment with the
head 5. Said wheels 10 are motor-driven so as to propel the current
postal item downstream from the unstacker device. They are made of
an elastically deformable elastomer material so that they are
suitable for adapting to accommodate various thicknesses of postal
item.
For the remainder of the sorting process, it is necessary for the
postal items to be put into series on exiting from the unstacker
device with a constant pitch between consecutive postal items. The
drives of the perforated belt 9 and of the suction nozzles are thus
actuated and stopped at a constant rate.
That processes of unstacking is repeated as another postal item at
the front of the stack is presented facing the unstacking head
5.
In the device of Document FR 2 797 856, the postal items from the
stack are put into series continuously, i.e. at a constant
unstacking rate.
In general in a postal sorting machine, the postal items exiting
from the unstacker are conveyed in series and on edge so as to be
taken past a read head. The read head acquires an image of each
postal item in the series for the purpose of automatically decoding
the inward sorting or outward sorting address of the postal item by
means of Optical Character Recognition (OCR) processing. The postal
items are then directed to the sorting outlets corresponding to the
automatically decoded addresses.
In that type of unstacker device it has been observed that a
significant proportion of postal items are not appropriately
presented facing the unstacking head while they are being unstacked
and might therefore be damaged or torn, e.g. on being engaged by
the wheels 10. Such postal items might even cause a jam in the
unstacker device, requiring a maintenance operator to take action
and the unstacker device to be stopped. Such action is costly and
slows down the overall sorting process. Such a situation can be
particularly frequent with open postal items of the advertising
brochure type or of the magazine type, etc.
Patent Document EP 0 562 954 presents a solution to that problem.
In that document, the feed device of the unstacker is similar to
the above-described device but further comprises a motor-driven
drop-forming feed. The motor-driven drop-forming feed is disposed
between the conveyor belt and the unstacking head. The effect of
the presence of said motor-driven drop-forming feed is to fan out
some of the first postal items (those postal items that are in the
drop-forming feed), thereby resulting in the first postal item at
the front of the stack being parted from the other postal items and
thus finding it easier to be presented appropriately against the
unstacking head 5.
In Document EP 0 562 954, presence sensors are provided that are
disposed so as to detect a certain inclination of fanning of the
postal items in the drop-forming feed and also so as to detect the
level of filling of the drop-forming feed. In response to the
signals delivered by the sensors, the motor-driven drop-forming
feed and/or the conveyor belt are actuated so as to fill the
drop-forming feed and/or so as to incline the postal items
appropriately.
However, the above-indicated features do not completely eliminate
situations in which the postal items are damaged or situations in
which a jam forms in the unstacker device, e.g. when very flexible
postal items tend to collapse in the drop-forming feed.
Patent Document WO 2005/042386 describes a postal item unstacker
device of the "shingler" type that is provided with a main magazine
comprising a main conveyor belt and a paddle, and a secondary
conveyor belt disposed between the main conveyor belt and the
unstacking head. The unstacking head includes a belt having a
motor-driven drive that is actuated so as to separate a current
first postal item from the stack and so as to eject said postal
item in a direction that is transverse to the direction of movement
of the postal items. In an unstacker device of the shingler type,
the belt of the unstacking head does not co-operate with a suction
chamber since the postal items are displaced one on another so as
to form a shingle pattern during the unstacking process.
In Document WO 2005/042386, sensors disposed in the unstacking head
make it possible to detect the inclination of the current postal
item to be unstacked and, in response to the signals delivered by
its sensors, the main conveyor belt, the paddle, or the secondary
conveyor belt are controlled so as to correct the inclination. In
addition, the motor-driven drive of the unstacking head is actuated
and stopped in a manner such as to obtain a constant pitch between
postal items at the outlet of the unstacker device.
With the device of Document WO 2005/042386, postal item damage
situations or jam situations are still too many.
Document US 2002/153654 also discloses a device for unstacking flat
objects with presentation control means for controlling how the
objects are presented facing an unstacking head, that device being
provided with one or two sensors disposed in the unstacking head.
Said control means stop the unstacking head when the one or two
sensors determine inappropriate presentation of an object.
Unstacking of said object is actuated when the presentation of the
object becomes appropriate, after the presentation of the object
has been corrected. However, with that device, an unacceptable
number of postal items are damaged and jam situations are
frequent.
OBJECTS AND SUMMARY OF THE INVENTION
An object of the present invention is thus to improve further a
device for unstacking flat objects so as to avoid said flat objects
being damaged and so as to avoid the unstacker device jamming.
To this end, the invention provides an unstacker device for
unstacking flat objects, which device comprises a motor-driven feed
magazine controlled so as to move flat objects in a stack and on
edge facing an unstacking head provided with a motor-driven drive
having a perforated belt and a suction chamber, which motor driven
drive is actuated so as to separate a current first object from the
stack and so as to eject it in a direction that is transverse to
the direction in which the stack of flat objects is moved, in which
device the motor-driven drive is actuated and stopped each time a
current object is unstacked, and the stack of flat objects is
straightened up in the magazine in response to detection of signals
delivered by a plurality of sensors disposed in the unstacking
head, wherein said sensors are disposed in the unstacking head in a
manner such as to deliver signals indicating that said current
object is presented appropriately relative to the unstacking head,
and wherein the drive of the unstacking head is actuated if the
signals indicate that the current object is presented
appropriately.
With this arrangement, it can be understood that the current postal
item in a stack of postal items can be unstacked only when said
current postal items is presented appropriately relative to the
unstacking head, thereby making it possible to avoid situations in
which the postal items are damaged and/or jam the device.
The unstacker device of the invention may include the following
features: the plurality of sensors includes a first sensor disposed
in the unstacking head to detect presence of a bottom portion of
the current object facing the unstacking head; the plurality of
sensors includes a second sensor disposed in the unstacking head to
detect presence of a first intermediate portion of the current
object facing the unstacking head, said first intermediate portion
being situated above said bottom portion of the current object; the
plurality of sensors includes a third sensor disposed in the
unstacking head to detect presence of a second intermediate portion
of the current object facing the unstacking head, said second
intermediate portion being situated above said first intermediate
portion of the current object; and the plurality of sensors further
includes a fourth sensor disposed to detect presence of a flat
object in said direction that is transverse to the direction in
which the stack of flat objects moves.
In a particular embodiment of the invention, the first sensor is a
flag mechanical sensor, the second sensor is a reflection optical
sensor, the third sensor is a reflection optical sensor, and the
fourth sensor is an optical barrier sensor, and the first, second,
and third sensors are aligned vertically in the unstacking
head.
In a particular embodiment of the invention, the feed magazine
comprises a drop-forming feed disposed between a main conveyor belt
with a motor-driven drive and the unstacking head, and a paddle
with a motor-driven drive, said paddle being suitable for being
moved along the main conveyor belt, the drop-forming feed being
provided with secondary conveyor belts with a motor-driven drive,
the control unit acting on the motor-driven drives of the main
conveyor belt, of the paddle, and of the secondary conveyor belts
so as to present the current object appropriately relative to the
unstacking head.
It should be understood that the main conveyor belt, the
motor-driven paddle, and the secondary conveyor belts in the
drop-forming feed are designed to be controlled asynchronously by
the control unit which is also arranged to change the speeds and
the directions of the motor-driven drives of the feed magazine in
order to present the current object appropriately.
In another particular embodiment of the invention, the control unit
is arranged to trigger an alarm at the end of a certain lapse of
time for which the control unit has been acting on the motor-driven
drives of the main conveyor belt, of the paddle, and of the
secondary conveyor belts without obtaining appropriate presentation
of the current object relative to the unstacking head.
The invention also provides a machine for handling postal items,
said machine including such an unstacker device.
The feed device of the invention is applicable to flat objects,
e.g. to small-format and large-format flat postal items, but it can
also be applied to fields for handling other flat objects such as
books, checks, or other objects.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention can be understood more clearly on reading the
following description with reference to the drawings. The
description is given merely by way of indication that in no way
limits the invention. In the drawings:
FIG. 1 diagrammatically shows a feed device for a prior art
unstacker for unstacking flat postal items;
FIG. 2 diagrammatically shows a feed device for an unstacker of the
invention for unstacking flat postal items;
FIG. 3 is a flow chart showing the various steps in the process of
checking the signals delivered by the sensors;
FIG. 4 diagrammatically shows the unstacking face with the sensors,
including the flag mechanical sensor;
FIG. 5 shows a first situation of inappropriate presentation of the
current postal item relative to the unstacking head;
FIG. 6 shows a second situation of inappropriate presentation of
the current postal item relative to the unstacking head;
FIG. 7 shows a third situation of inappropriate presentation of the
current postal item relative to the unstacking head;
FIG. 8 shows a fourth situation of inappropriate presentation of
the current postal item relative to the unstacking head;
FIG. 9 shows a fifth situation of inappropriate presentation of the
current postal item relative to the unstacking head;
FIG. 10 shows a sixth situation of inappropriate presentation of
the current postal item relative to the unstacking head;
FIG. 11 shows a seventh situation of inappropriate presentation of
the current postal item relative to the unstacking head; and
FIG. 12 is a table showing the signals from the sensors detecting
an inappropriate presentation of the current postal item to be
unstacked.
FIG. 1 is presented in the above description of the prior state of
the art.
FIG. 2 thus shows an unstacker device 1 of the invention for
unstacking postal items such as letters and large-format flat
postal items or "flats", the elements that are in common with the
device of FIG. 1 bearing identical numerical references.
MORE DETAILED DESCRIPTION
The unstacker device serves to put the postal items into series
upstream from conveyor belts, in which series of postal items the
postal items are separated in pairs with a normally constant pitch.
The motor-driven deformable wheels 10 between which the postal
items put into series are nipped can be caused to be driven at
variable speed so as to take up differences in pitch between
consecutive postal items, where necessary. This variable-speed
arrangement constitutes a synchronization system that guarantees a
constant pitch.
Advantageously, the synchronization system authorizes certain
correction operations to be performed during a time window T
compatible with the requirement for constant pitch between
consecutive items at the outlet of the unstacker device.
The unstacker device 1 includes a main feed magazine 1 with a
motor-driven conveyor belt 2 on which postal items 3 are disposed
in a stack and on edge in front of a motor-driven paddle 4 that
extends substantially in a vertical plane while being slightly
inclined so as to support the back of the stack of postal
items.
The conveyor belt 2 and the paddle 4 move the stack of postal items
3 on edge towards the unstacking head 5 in the direction 6.
A jogging edge 7 against which the side edges of the postal items
are aligned is also shown along the conveyor belt 2.
FIG. 2 shows a channel-shaped drop-forming feed 11 constituting a
secondary feed magazine between the end of the main conveyor belt 2
and the unstacking head 5. The bottom of the drop-forming feed 11
is situated at a distance of about 100 millimeters (mm) below the
top surface of the conveyor belt 2 and has a width of about 98 mm
in the direction 6.
The bottom of the drop-forming feed 11 is provided with a set of
motor-driven secondary conveyor belts 12, e.g., as in this example,
four conveyor belts, which secondary conveyor belts move the postal
items on edge inside the feed in direction 6 towards the unstacking
head 5.
The motor-driven unstacking head 5 extends vertically from the
bottom of the drop-forming feed 11 to a sufficient height
corresponding to at least the maximum height of the postal items to
be unstacked.
The unstacking head 5 in the form of a metal sheet is, in this
example, provided with two rectangular openings disposed
side-by-side in the direction 8. In each of the openings, an
endless perforated belt 9 co-operates with suction chambers or
suction nozzles (not shown) to take hold of a current postal item
from the stack that is facing the head, and to move said current
postal item in the direction 8.
In accordance with the invention, the motor-driven drives for
driving the conveyor belt 2, the paddle 4, the secondary conveyor
belts 12, and the unstacking head (perforated belts 9 and suction
nozzles) are designed to be controlled independently from one
another, but naturally they can be controlled in a manner such as
to be synchronized relative to one another by a control unit 13,
e.g. a programmable data processor.
In FIG. 2, for reasons of clarity, only one monitoring/control link
is shown between the control unit 13 and a conveyor belt 12, but
naturally the unit 13 is also connected by monitoring/control links
to the respective motor-driven drives of the conveyor 2, the paddle
4, and of the belts 9 (and suction nozzles).
In accordance with the invention, the unstacker device is provided
with a set of sensors, each of which delivers a detection signal to
the control unit 13. In FIG. 2, also for reasons of clarity, only
one monitoring link is shown between the control unit 13 and a
sensor, but naturally the unit 13 is also connected by monitoring
links to the other sensors used in accordance with the invention as
described below.
More particularly, FIG. 2 shows first sensors 20, 21, and 22 that
are disposed in vertical alignment in the unstacking head 5, and,
in this example, between the two openings in the head, in which
openings the perforated belts 9 act.
The sensor 20 that is disposed lowest in the unstacking head 5 at
the bottom of the drop-forming feed 11 is, in this example, a flag
mechanical sensor in the form of a finger that is retractable into
the thickness of the head 5 for the purpose of detecting the
presence of a postal item facing the lowest portion (bottom) of the
head 5.
The sensor 20 is shown in more detail in FIG. 4. It delivers a
signal indicating the presence of a postal item when it is
retracted far enough into the head under the effect of the thrust
from the base of the current postal item in the direction 6, which
current postal item is itself pressed by the stack of postal items
bearing against one another in the drop-forming feed 11. More
particularly, in the rest position, the sensor 20 has a free end
that projects relative to the unstacking head and that has a
bevel-shaped profile flaring in the direction 6 and whose flat
portion comes flush with the bottom of the drop-forming feed 11.
The sensor 20 moves in the direction 6 against the drive from a
return spring R, and the signal that it delivers, when it is
retracted into the unstacking heads 5, can also indicate the
distance over which it has retracted relative to its rest position,
and thus indicate a pressure magnitude. It can be seen in FIG. 4
that said sensor is disposed below the bottom line of the
perforated belts 9.
The sensor 20 is adapted to measure the pressure exerted by the set
of postal items in the drop-forming feed at the bases of the postal
items. A pressure of 0.3 newtons from the bases of the postal items
against the unstacking head fans the postal items in the
drop-forming feed out into a fan that is upwardly open. Fanning out
the postal items facilitates separating them and reduces the rate
of occurrences of postal items being taken in bunches instead of
one-by-one. Provision can be made to monitor the pressure from the
bases of the postal items, and said pressure can be adjusted by
feeding the drop-forming feed 11 with postal items.
The sensor 21 is a reflection photoelectric cell disposed
vertically above the sensor 20, e.g. 20 mm from the bottom of the
drop-forming feed, for detecting presence of a current postal item
facing a first intermediate portion of the head above the bottom
portion of the head.
The sensor 22 is a reflection photoelectric cell disposed
vertically above the sensor 21, e.g. 90 mm from the bottom of the
drop-forming feed, for detecting the presence of a current postal
item facing a second intermediate portion of the head above the
first intermediate portion. As shown in FIG. 4, the two
intermediate portions are at the same level as the perforated belts
9.
The sensors 20 and 21 are set so that each of them delivers a
signal indicating presence of a postal item when said postal item
is at a distance less than about 4 mm from the head 5 in the
direction 6.
The sensor 22 is set to deliver a signal indicating presence of a
postal item when said postal item is at a distance less than about
8 mm from the head 5 in the direction 6.
It can thus be understood that the signals delivered by the sensors
20 to 22 normally indicate together the presentation of the current
postal item to be unstacked relative to the unstacking head.
FIG. 2 also shows three other sensors 23, 24, and 25.
The sensor 23 is a barrier photoelectric cell that operates along
the unstacking head 5 and whose beam is directed to cross the face
of a postal item. Said beam is launched substantially in the
direction 8 between an emitter and a receiver of the sensor 23 at
about 8 mm upstream from the unstacking head 5 relative to the
direction 6 and at a height of about 190 mm from the bottom of the
drop-forming feed 11.
FIG. 2 shows a single element of the sensor 23 (emitter or
receiver) mounted on a side of the unstacking head that is opposite
from the side on which the deformable wheels 10 are disposed. It
should be understood that the complementary other element of the
sensor 23 is disposed on the other side of the head, and, in this
example, on the same side as the inlet cone upstream from the
motor-driven deformable wheels 10. The sensor is disposed so as to
detect presence of a flat object in said direction indicated by the
arrow 8.
The sensor 24 is also a barrier photoelectric cell identical to the
sensor 23 but whose emitter and reflector are disposed at a height
of about 112 mm relative to the bottom of the drop-forming feed and
in a transition zone between the main conveyor belt 2 and the
drop-forming feed 11 on either side of the magazine 1. The signal
delivered by the sensor 24 indicates presence of postal items in
the drop-forming feed.
The sensor 25 can be a mechanical-contact sensor disposed so as to
detect presence of the paddle 4 at the transition zone between the
main conveyor belt 2 and the drop-forming feed 11.
Finally, FIG. 2 shows two other sensors 26 and 27 (a single
component (emitter or receiver) of each of these sensors is shown)
that are barrier photoelectric cells disposed vertically one above
the other and whose beams are directed in the direction indicated
by arrow 6 in order to detect presence of postal items in the inlet
cone in the vicinity of and upstream from the deformable wheels
10.
The use of the various sensors is described in more detail below
for various situations of inappropriate presentation of the postal
items facing the unstacking head.
FIG. 3 is a simplified flow chart showing how the unstacker device
of the invention operates with the sensors and more particularly
how the control unit 13 operates.
In preparation step 31, postal items are placed by the operator in
a stack and on edge on the main conveyor belt 2 in front of the
paddle 4. The control unit actuates all of the motor-driven drives
for operation at a constant unstacking rate. The speeds of movement
of the conveyor belt 2 and of the paddles 4 are identical. The
speed of movement of the conveyor belts 12 is slightly higher than
the speed of movement of the conveyor belt 2 or of the paddle. The
speed of movement of the belts 9 is much higher than the speed of
movement of the conveyor belts 12. By way of example, in normal
unstacking mode, the speed of conveyor belt 2 is 0.096 meters per
second (m/s), the speed of conveyor belts 12 is 0.152 m/s, and the
speed of the perforated belts 9 is 1.5 m/s.
The stack of postal items 3 on edge thus advances towards the
unstacking head 5 and first postal items at the front of the stack
fall into the drop-forming feed 11. In this example, the stack of
postal items is thus fractured and the postal items on edge in the
drop-forming feed are fanned out under the action of the faster
movement of the conveyor belts 12 in the bottom of the drop-forming
feed, and a current first postal item to be unstacked is detected,
e.g. by the sensor 23.
At this stage, the process continues with step 32 where the signals
S delivered by the sensors are checked by the control unit 13 for
determining whether the current postal item to be unstacked has a
presentation relative to the unstacking head that is appropriate
for said current postal item to be unstacked without any risk of
damage or jamming.
If, in step 32, the signals S from the sensors indicate that the
presentation of the current postal item is appropriate and that the
current time lies within the time window T that is compatible with
a constant pitch, then, in step 33, the control unit 13 keeps the
conveyor belt 2, the paddle 4, and the conveyor belts 12 in normal
unstacking operation, and actuates the motor driven drives for
driving the perforated belts 9 and the suction nozzles so as to
unstack the postal item. The current postal item is then put into a
series by passing between the deformable wheels 10, the
motor-driven drives for driving the perforated belts 9 and the
suction nozzles are stopped and the process loops back to step 32
for another check on the signals S. In this looped process, the
postal items are unstacked at a constant rate of one postal item
every 330 milliseconds.
If, in step 32, the signals S delivered by the sensors indicate
that the current postal item is inappropriately presented relative
to the unstacking head 5, the process continues with step 34 in
which the control unit 13 triggers a correction stage for
correcting the presentation of the current postal item relative to
the unstacking head. It can be understood that, since the
motor-driven drives of the perforated belts 9 and of the suction
nozzles are stopped, the current postal item is not unstacked.
In order to perform this correction, in accordance with the
invention, the control unit 13 controls the motor-driven drives of
the conveyor belt 2, of the paddle 4, and of the conveyor belts 12
of the drop-forming feed independently in a manner such as to
straighten up the postal items that are in the drop-forming feed
11, and thus such as to correct the presentation of the current
postal item to be unstacked.
The manner in which the straightening up is performed is described
in detail below.
During the correction stage triggered in step 34, the unit 13
checks, in step 35, the signals S delivered by the sensors to the
control unit 13 so as to determine whether the current postal item
is then presented appropriately relative to the unstacking head. In
practice, the steps 34 and 35 can be performed almost
simultaneously.
If, in step 35, the signals S from the sensors indicate that the
current postal item to be unstacked is presented appropriately, and
that the current time lies within the time window T compatible with
a constant pitch between consecutive postal items at the outlet of
the unstacking device, then the control unit 13 continues the
process with step 36 by actuating the motor-driven drives of the
unstacking head (perforated belts and suction belts).
The current postal item to be unstacked is then put in a series
between the deformable wheels 10 at the outlet of the unstacking
device, the motor-driven drives of the perforated belts 9 and of
the suction nozzles are stopped, and normal unstacking operation is
resumed. The process then loops back to step 32.
In step 35, if the signals S from the sensors indicate that the
current postal item to be unstacked is not presented appropriately
and/or that the current time lies outside the time window T, the
process loops back to step 34 so as to continue the correction
stage or so as to adapt the correction as a function of the signals
S.
Therefore, the steps 34 and 35 are repeated as many times as
necessary until appropriate presentation of the current item to be
unstacked is obtained within the time window T, but preferably,
beyond a certain correction time without appropriate presentation
being obtained, an alarm is triggered in order to indicate that
manual action is necessary.
In accordance with the invention, the current postal item to be
unstacked being presented inappropriately relative to the
unstacking head 5 is detected on the basis of a check of the
signals delivered by the four sensors 20, 21, 22, and 23. The
current postal item to be unstacked being presented appropriately
is detected on the basis of a check of the signals delivered by the
same sensors 20, 21, 22, and 23.
The criteria for determining whether or not the current postal item
to be unstacked is presented appropriately relative to the
unstacking head can be codified in a truth table as shown in FIG.
12.
FIG. 12 shows said truth table with, on the left, a very
diagrammatic representation of the current postal item to be
unstacked, seen in profile, in correspondence with the value of the
signal delivered by the sensors 20 to 24. A signal at the value of
"1" indicates detection of presence of a postal item, whereas a
signal at the value of "0" indicates absence of detection of
presence of a postal item. The truth table also shows the commands
of the motor-driven drives of the conveyor belt 2, of the paddle 4,
and of the secondary conveyor belts 12 as a function of the signals
delivered by the sensors 20 to 24.
In certain inappropriate presentation situations detected by the
sensors, the control unit 13 can react by actuating the
motor-driven drive of the unstacking head only if the current
postal item is not already engaged in the inlet cone between the
deformable wheels 10 (as detected by the sensors 26 and 27). On
detecting slumped postal items in the drop-forming feed, it is also
possible for the control unit 13 not to actuate the motor-driven
drive during the time window T, so as to allow the time necessary
for straightening up said postal items by pushing them with the
postal items on the main conveyor. If the control unit 13 detects,
by means of the sensors, that only the base of the current postal
item is improperly presented, it is possible for it not to actuate
the motor-driven drive of the unstacking head during the time
window T, so that the conveyor belts 12 in the drop-forming feed
have time to rectify the presentation of said current postal
item.
The process of straightening up the postal items in step 34 of FIG.
3 can be even better understood from the following description of
various examples.
FIG. 5 shows a situation in which the postal items 3 in the
drop-forming feed 11 are slumping under their own weight, resulting
in the current postal item to be unstacked not bearing fully
against the unstacking head 5.
This situation is detected by the control unit 13 by the fact that
the sensor 22 generates a signal indicating absence of a postal
item while the sensors 20, 21, and 23 generate signals indicating
presence of a postal item. This situation corresponds to the third
row of the truth table of FIG. 12.
With reference to FIG. 3, for this example, in step 32, the control
unit 13 detects inappropriate presentation of the postal item to be
unstacked, and, in step 34, causes a correction stage to be
preformed for correcting the presentation of the current postal
item relative to the unstacking head.
In step 34, the control unit 13 controls the motor-driven drives of
the conveyor belt 2 and of the paddle 4 by causing them to go over
to slow speed of movement at 0.096 m/s. At the same time, the
control unit 13 suspends the motor-driven drive of the conveyor
belts 12, since, as indicated by the sensors 20 and 21, the base of
the current postal item is bearing correctly against the head 5,
thereby straightening up the postal items in the drop-forming feed
by means of new postal items arriving from the main conveyor belt 2
by being pushed by the paddle 4.
During the correction stage, the unit 13 checks the signals form
the sensors in step 35. In step 35, if the signals S from the
sensors indicate that the current postal item to be unstacked is
presented appropriately, and that the current time lies within the
time window T, the control unit 13 continues the process in step 36
by actuating the motor-driven drive of the unstacking head
(perforated belts and suction nozzles).
The current postal item to be unstacked is then put into a series
between the deformable wheels 10 at the outlet of the unstacking
device, the motor-driven drives of the perforated belts 9 and of
the suction nozzles are stopped, and normal unstacking operation is
resumed. The process then loops back to step 32.
Conversely, in step 35, if the signals S from the sensors indicate
that the current postal item to be unstacked is presented
inappropriately, the process loops back to step 34 so as to
continue the correction stage or so as to adapt the correction as a
function of the signals S.
In a situation (not shown) in which the sensors 21 and 23 deliver
signals indicating presence of a postal item while the sensors 20
and 22 deliver signals indicating absence of a postal item, then,
in step 34, the control unit 13 controls the conveyor belts 12 so
as to cause them to go over to medium speed at 0.152 m/s so as to
straighten up the postal items in the drop-forming feed 11. This
situation corresponds to the second row of the truth table of FIG.
12.
Another analogous situation would arise with sensors 20, 21, and 22
delivering signals indicating absence of a postal item while
sensors 23 and 24 deliver signals indicating presence of a postal
item. This situation corresponds to postal items tilting in the
left portion of the drop-forming feed in FIG. 5. In which case, the
control unit 13, in step 34, controls the conveyor belts 12 so as
to cause them to go over to medium speed at 0.152 m/s, and controls
the motor-driven drives of the conveyor belt 2 and of the paddle 4
by causing them to go over to slow speed of movement at 0.096 m/s.
This situation corresponds to the fourth row of the truth table of
FIG. 12.
A particular situation would arise with sensors 21 and 22
delivering signals indicating absence of a postal item while
sensors 20, 23, and 24 are delivering signals indicating presence
of a postal item. In which case, the control unit 13, in step 34,
controls the conveyor belts 12 so as to cause them to go over to
medium speed in reverse at 0.152 m/s, and controls the motor-driven
drives of the conveyor belt 2 and of the paddles 4 by causing them
to go over to slow speed of movement at 0.096 m/s. This situation
corresponds to the fifth row of the truth table of FIG. 12.
FIG. 6 shows another situation of the current postal item to be
unstacked being presented inappropriately relative to the
unstacking head. In this situation, the postal items in the
drop-forming feed 11 are flopping backwards at their tops, which
results in sensors 20, 21, and 22 delivering signals indicating
presence of a postal item but in sensor 23 delivering a signal
indicating absence of a postal item. This situation corresponds to
the seventh row of the truth table of FIG. 12.
In the example of FIG. 6, sensor 24 detects presence of a postal
item. In step 32, the control unit 13 thus detects an inappropriate
presentation of the current postal item relative to the unstacking
head 5. In step 34, the control unit 13 triggers a correction stage
consisting simultaneously in interrupting the drive of the conveyor
belt 2 for 25 milliseconds, in causing the speed of movement of the
paddle to go over to slow speed at 0.096 m/s, and in interrupting
the drive of conveyor belts 12 in the drop-forming feed. After a
time delay of 25 milliseconds, the unit 13 causes the speed of the
conveyor belt 2 to go over to 0.096 m/s.
This correction stage generates an offset between the paddle 2 and
the conveyor belt 2 straightening up the tops of the postal items
both on the main conveyor belt 2 and in the drop-forming feed
11.
During the correction stage, the unit 13 checks, in step 35,
whether the signals S from the sensors indicate that the current
postal item is presented appropriately, and whether the current
time lies within the time window T. In which case, in step 36, the
control unit 13 actuates the motor-driven drive of the unstacking
head and continues the process as described above.
Conversely, in step 35, if the signals S from the sensors indicate
that the current postal item is inappropriately presented, the
process loops back to the step 34 so as to continue the correction
stage or so as to adapt the correction as a function of the signals
S.
FIG. 7 shows another example of the current item to be unstacked
being inappropriately presented relative to the unstacking head. In
this example, the tops of the postal items in the drop-forming feed
are slumping backwards and, at the same time, the bases of the
postal items in the drop-forming feed are slipping backwards.
In this situation, sensors 20 and 23 deliver signals indicating
absence of a postal item while sensors 21, 22, and 24 deliver
signals indicating presence of a postal item. This situation
corresponds to the sixth row of the truth table of FIG. 12.
In step 34, the control unit 13 triggers a correction stage
consisting in suspending the drive of the conveyor belt 2 for 25
milliseconds, and then causes the speed of the conveyor belt 2 to
go over to 0.096 m/s. At the same time, the speed of movement of
the paddle 4 is caused to go to slow speed at 0.096 m/s while the
speed of the conveyor belts 12 is caused to go to medium speed at
0.152 m/s. This results both in straightening up the tops of the
postal items in the drop-forming feed and, at the same time, in
causing the bases of the postal items to advance towards the
unstacking head.
During the correction stage, the unit 13 checks, in the step 35,
whether the signals S from the sensors indicate that the postal
item is presented appropriately, and that the current time lies
within the time window T, and the process continues as described
above.
FIG. 8 shows another example of the postal item to be unstacked
being presented inappropriately relative to the unstacking head. In
this example, the bases of the postal items in the drop-forming
feed are set back relative to the unstacking head. Sensors 20 and
21 deliver signals indicating absence of a postal item, while
sensors 22 and 23 deliver signals indicating presence of a postal
item. Sensor 24 also delivers a signal indicating absence of a
postal item in the drop-forming feed. In which case, the
drop-forming feed is insufficiently fed with postal items. This
situation corresponds to the ninth row of the truth table of FIG.
12.
In step 34, the control unit 13 triggers a correction stage
consisting in causing the conveyor belt 2 and the paddle 4 to go
over to slow speed at 0.096 m/s while the conveyor belts 12 are
caused to go over to medium speed at 0.152 m/s.
This also results in the drop-forming feed 11 being fed with postal
items by packing the postal items more tightly in the drop-forming
feed. As a result, the postal item to be unstacked is straightened
up.
FIG. 9 shows yet another example of inappropriate presentation of
the current postal item relative to the unstacking head.
In this example, sensors 21 and 24 deliver signals indicating
absence of a postal item while sensors 20, 22, and 23 deliver
signals indicating presence of a postal item. This situation
corresponds to the tenth row of the truth table of FIG. 12.
In step 34, the control unit 13 causes the paddle 4 and the
conveyor belt 2 of the main magazine to go over to slow speed at
0.096 m/s, while it causes the conveyor belts 12 to move in reverse
at the medium speed of 0.152 m/s.
This results both in feeding the drop-forming feed 11 with postal
items, and also in moving the bases of the postal items that are
already present in the drop-forming feed 11 backwards, thereby
straightening up all of the postal items in the drop-forming feed
11.
FIG. 10 shows yet another example of the current postal item to be
unstacked being presented inappropriately relative to the
unstacking head.
In this example, sensors 20, 21 deliver signals indicating absence
of a postal item while sensors 22, 23, and 24 deliver signals
indicating presence of a postal item. This situation corresponds to
the eleventh row of the truth table of FIG. 12.
In this example, the drop-forming feed is overfed with postal items
whose bottoms slip back.
In step 34, the control unit 13 causes the conveyor belt 2 and the
paddle 4 to go over to slow speed at 0.096 m/s for 25 milliseconds
and then interrupts operation of them. At the same time, the
control unit causes the conveyors 12 to go over to medium speed at
0.152 m/s so as to straighten up the postal items in the
drop-forming feed, without feeding the drop-forming feed with any
more postal items.
In FIG. 11, the presentation of the postal items is analogous to
the situation in FIG. 10, but the bases of the postal items are
slipping forwards. Sensor 21 delivers a signal indicating absence
of a postal item while sensors 20, 22, 23, and 24 deliver signals
indicating presence of a postal item. This situation corresponds to
the twelfth row of the truth table of FIG. 12.
In this situation, the control unit 13 causes the conveyor belt 2
and the paddle 4 to go over to slow speed for 25 milliseconds and
then interrupts operation of them. At the same time, it causes the
conveyor belts 12 to go over to reverse at the speed of 0.152 m/s
so as to straighten up the postal items in the drop-forming
feed.
Naturally, the invention is not limited to the embodiment of the
unstacker device that is described above. In particular, it is
possible, while remaining within the ambit of the invention, to
modify the details of the sensors, to modify the number and the
positions of the sensors, and to apply different corrections in
response to the signals delivered by the sensors.
* * * * *